1. Field of the Invention
The present disclosure relates to an image forming apparatus.
2. Description of the Related Art
There are electrophotographic type image forming apparatuses, such as printers, copying machines, facsimile devices, and composite machines combining these functions, which use developing apparatus based on various different development methods. More specifically, for example, the developing methods are divided broadly into a dry developing method and a wet developing method, depending on the type of developer used. Of these, a developing apparatus based on a wet developing method employs a liquid developer in which toner particles and colored particles of pigment, or the like, are dispersed in a carrier liquid. In a developing apparatus using a wet developing method, charged coloring particles in the liquid developer move from the surface of a developing roller to the surface of a photosensitive drum, due to the principle of electrophoresis, and by this means, an electrostatic latent image formed on the surface of the photosensitive drum, which is an image carrier, is converted into a real image.
Furthermore, in an image forming apparatus which uses an electrophotographic method, if a developing containing coloring particles having relatively small particle size is used, then it is considered possible to form high-quality images having excellent tonality and high resolution. However, with a dry developer, the coloring particles tend to be scattered more readily in the air, if the coloring particles have a small particle size. On the other hand, in a liquid developer, coloring particles are distributed in a carrier liquid, and therefore it is possible to sufficiently suppress scattering of the coloring particles into the air. For this reason, it is desirable to use coloring particles having a small particle size, which cannot be adequately prevented from scattering when in a dry developer, for example, even microscopic coloring particles having an average particle size of the sub-micron order. Therefore, since an image forming apparatus equipped with a wet developing type of developing apparatus can use a liquid developer containing coloring particles of relatively small average particle size of this kind, then the formation of high-quality images having excellent tonality and high resolution can be expected.
Furthermore, among image forming apparatuses which use liquid developer, there are image forming apparatuses which include an intermediate transfer body, such as an intermediate transfer belt, for receiving the temporary transfer (primary transfer) of a coloring particle image which has been formed on a photosensitive drum, onto a circumferential surface of the belt, and then transferring the coloring particle image onto a recording medium (secondary transfer). An image forming apparatus which transfers a coloring particle image formed on a photosensitive drum, onto a recording medium, by means of an intermediate transfer body of this kind, recovers liquid developer remaining on the intermediate transfer belt after secondary transfer, from the intermediate transfer belt.
For example, apparatuses such as the following have been reported as image forming apparatuses of this kind.
Firstly, there has been reported a liquid developing electrophotographic apparatus using a liquid developer, in which a cleaning device for removing residual developer remaining on an intermediate transfer belt is provided to the upstream side of a developing apparatus and to the downstream side of a pressurization roller provided so as to oppose the intermediate transfer body in order to transfer a toner image onto a print medium, wherein the cleaning device includes: a carrier liquid application device which applies carrier liquid to the intermediate transfer body after transferring the image to the print medium; a bias voltage application device which applies a bias voltage of opposite polarity to the charging properties of the toner particles in the developer, to the intermediate transfer body; and a recovery device which recovers residual toner by removing, from the intermediate transfer body, carrier liquid that has been applied by the carrier liquid application device and liquid developer remaining on the intermediate transfer body which has not been transferred to the print medium.
Moreover, there has also been reported an image forming apparatus using a liquid developer having an intermediate transfer body, in which a liquid application member for applying liquid to the intermediate transfer body is provided between a secondary transfer position of transfer from the intermediate transfer body to a transfer medium and a cleaning position where a cleaning member abuts against the intermediate transfer body to the downstream side of the secondary transfer position in the direction of rotation of the intermediate transfer body.
Furthermore, there has also been reported an image forming apparatus using a liquid developer having an intermediate transfer body, in which a liquid application member for applying liquid having a lower viscosity than the carrier liquid to the intermediate transfer body is provided between a secondary transfer position of transfer from the intermediate transfer body to a transfer medium and a cleaning position where a cleaning member abuts against the intermediate transfer body to the downstream side of the secondary transfer position in the direction of rotation of the intermediate transfer body.
Moreover, there has also been reported an image forming apparatus using a liquid developer having an intermediate transfer body, in which a liquid application member for applying a portion of developer recovered by a cleaning member is provided between a secondary transfer position of transfer from the intermediate transfer body to a transfer medium and a cleaning position where the cleaning member abuts against the intermediate transfer body to the downstream side of the secondary transfer position in the direction of rotation of the intermediate transfer body.
As described previously, a liquid developer uses coloring particles having relatively small average particle size, in order to form an image of high quality. On the other hand, the smaller the particle size of the coloring particles, the greater the relative surface area and the higher the adhesive force acting on the intermediate transfer body, and the like. For this reason, in an image forming apparatus which includes an intermediate transfer body, it is considered that liquid developer is liable to remain on the intermediate transfer body after secondary transfer. Furthermore, the liquid developer remaining on the intermediate transfer body after secondary transfer is considered to affect image formation.
Therefore, in order to form images of high quality, it is necessary to be able to suitably clean away developer remaining on the intermediate transfer body after secondary transfer.
According to the first prior art apparatus described above, it is stated that aggregated or solidified liquid developer on the intermediate transfer body can be cleaned in an effective and stable manner.
Furthermore, according to the second to fourth prior art apparatuses described above, it is disclosed that adhering matter attached to the intermediate transfer body can be cleaned away easily.
However, in prior art image formation apparatuses such as those described above, there are cases where cleaning of the liquid developer remaining on the intermediate transfer body after secondary transfer is inadequate. For example, there are cases where cleaning of the liquid developer is inadequate, not only when using a liquid developer containing toner which includes a binding resin and a pigment, and the like, as the coloring particles, but also, for instance, when using a liquid developer in which a coloring material, such as pigment or the like, is dispersed in a carrier liquid in which resin is dissolved.